No. NOT Alienware. Quick, somebody shoot me. Dells are nothing but ovens disguised as a pc, with hundreds of dollars worth of absolutely worthless warranty added and a tech support that's worse.
Best bang for the buck pc is ibuypower, if you don't mind having to tinker to get it all dialed in and re-doing some cable management and possibly/probably minor repairs like reseating ram or changing fan headers etc. But you'll actually get the parts.
Best quality build is MainGear. Best tech support, best out of the box performance, pretty much you get a dream pc to be proud to take pictures of. But you'll spend more to get the same components as an ibuypower. But you can also opt for extras like etched TG with your logo or case painted (automotive grade paint) etc. Not something the cheaper boutiques offer.
HP is somewhere in between, along with most boutique builders like Origin, CyberPowerPC etc.
For that stereo case, I'd forget about ATX as a form factor. Start thinking mITX, small form factor builds. An SFX psu isn't much bigger than a couple of cigarette packs stacked, but will make life immeasurably easier, as will the 6in x 6in mITX motherboard vs a 9in x 13in ATX. You are limited not only by case size restraints but cooling necessity, that requires airflow and packing in the components reduces that significantly. So space saving is a must. Or you'll be needing a 8k rpm Delta server fan just to get air from one side of the shell to the other.